Correct `special_tokens_mask` when `add_special_tokens=False` (#2965)
Correct `special_tokens_mask` when `add_special_tokens=False` (#2965)

Don't know of a use case where that would be useful, but this is more consistent
huggingface/transformers,huggingface/transformers,huggingface/transformers,huggingface/pytorch-transformers,huggingface/transformers